The long-term goal of this study is to expand our knowledge of the early development of arousal, attentional and affective behaviors, especially as they are shaped by culturally specific caretaking practices. The research design will capitalize on a natural experiment in parallel communities in the Netherlands and the USA. Two groups of infants (60 in each community) will be followed from shortly after birth until age 2 years. Assessment procedures include parent interviews, diaries, and actigraph recordings of daily activities and rest, samples of salivary cortisol at specified times of the day, behavior observations in the home, parental ratings of temperament, evaluation of reactivity and adaptation to developmentally appropriate challenges, and reactions to DPT inoculations. Included for these latter two procedures is monitoring of autonomic nervous system functioning (heart rate) and endocrine functioning (cortisol). The project has three specific goals: 1) To replicate and extend, with a longitudinal design, conclusions established in previous cross-cultural comparisons regarding community differences in the amount and patterning of sleep, daytime arousal, management of attention, and affective expression during the first two years of life. These differences appear to correspond to the way parents in the two communities interact with their babies and organize daily life for them; 2) To examine in greater detail the involvement of biologic mechanisms in the developmental pathways identified, particularly those involving autonomic functioning and activity of the hypothalamic-pituitary-adrenal axis; 3) To arrive at a clearer understanding of diversity in normative biobehavioral development as regulated through cultural processes. The product of this study will be new knowledge about how culturally organized environments interact over time with developing biological and behavioral systems to yield specific developmental outcomes. The results will inform current discussion about the causes of poor arousal regulation, attentional difficulty, sleep deprivation, and their consequences for social, cognitive, and self-regulatory functioning in the preschool years.